Daclizumab is known to block the alpha-chain (CD25) of the IL-2 receptor which is required for T cells to sense signals from T cell growth factor, IL-2. One of the arguments that was thought that might be against the application of Daclizumab was that IL-2 signaling was critical for activation induced cell death (AICD). Blockage of AICD could result in decreased apoptosis and increased lymphoproliferation. But clinical data proved that Daclizumab indeed ameliorated autoimmune uveitis and was an excellent alternative therapy. One of the hypotheses would be that in vivo blockage of CD25 in humans differ from inactivation of CD25 gene in mice. Multiple mechanisms could be contributing to Daclizumab effects besides its role in blocking IL-2 receptor. We continuousely monitored a group of patients who underwent Daclizumab therapy. We found that a sub-group of NK cells, called CD56bright, were induced in vivo after Daclizumab infusion. We showed that these cells secreted large amount of IL-10 and could be regulatory NK cells. We proposed that these induced CD56bright NK cells under Daclizumab therapy may be beneficial to the clinical outcome of uveitis patients. FoxP3 and the immune response. The purpose of this investigation was to evaluate CD4+Foxp3 regulatory T cell populations in patients with endogenous, non-infectious uveitis and to determine if correlates existed between regulatory T cell populations and clinical disease characteristics. Patients with non-infectious intermediate, posterior, and panuveitis were evaluated for CD4+Foxp3+ T-regulatory cell populations with flow cytometry. 20 patients with intermediate, posterior and panuveitis were evaluated. A borderline statistically significant difference in median percentages of CD4+Foxp3+ T-regulatory cells was observed when comparing patients with active versus inactive disease (p = 0.047). No differences were observed between systemic autoimmune condition versus isolated ocular diagnoses (p = 0.12) and between patients with and without cystoid macular edema (p=0.43). Two patients with particularly severe disease who were recalcitrant to multiple immunosuppressive therapies were observed to have <1% CD4+Foxp3+ lymphocyte populations. RT-PCR revealed extremely low levels of Foxp3 mRNA expression suggesting that the depletion of CD4+Foxp3+ T-regulatory cells was mediated at the transcriptional level. T-regulatory cell populations do not appear to differ between uveitis patients with and without associated systemic autoimmune diseases or cystoid macular edema. The identification of severely depleted CD4+Foxp3+ cell populations and Foxp3 mRNA transcripts in two patients with recalcitrant ocular inflammatory disease suggests that loss of CD4+Foxp3+ T-regulatory cell populations may be a salient feature in some cases of severe ocular inflammation. Subtypes of Macrophages and Interaction of Macrophages with the RPE. In collaboration with Dr. Siamon Gordon in Oxford and Dr. Miller at the NEI, we have initiated studies on human macrophages focusing on 1) the interaction of human macrophages with human retinal pigmented epithelial cells and 2) phenotypic and functional heterogeneity of human macrophages and its implication in autoimmune intraocular inflammatory diseases. We have found that human RPE cells can interfere with the normal processes of differentiation and maturation of macrophages. Immune factors leading to CNV By adapting and modifying a commonly used laser induced CNV mouse model, we have established a strategy to investigate the involvement and potential mechanisms of immune responses in CNV, the most common complication in AMD and other important eye diseases. We have combined flow cytometry, vibrotome immunohistochemistry and flat-mount techniques plus confocal immunomicroscopy to evaluate the model. We have discovered that there is a dynamic and complex movement of immune cells during the development ofCNV in the mouse. Immune cells that are involved in CNV include neutrophils, monocytes, macrophages, NK cells and microglial cells. There is an apparent differential influx of immune cells in that neutrophils and NK cells move in very early followed by macrophages and microglial cells. The macrophages and microglial cells are present as long as 2-months after laser induced CNV. In addition, by using gene knock-out mice and therapeutic intervention using defined biological reagents, we have found that T cells and B cells are probably not important for the early development of CNV in this mouse model. Complement and the immune response. Several reports have associated SNPs of complement factor H with either susceptibility to or protection against AMD. This association has been attributed to involvement of the innate immune system, presumably through macrophage activity and Toll-like receptors. We have looked at this question differently;rather that complement and its components may be part of the acquired immune system. Initial observations have demonstrated that immune cells, both T cells and macrophage lineage cells such as dendritic cells, from AMD have enhanced C5r and C3r expression, which occurs before T cell activation.